In my U.S. Pat. Nos. 3,036,388 (since reissued as Re. 25,363 and Re. 25,822), 3,406,363, 3,460,248 and 3,938,263 there are described multi-colored micromagnets and rotatable multi-colored micromagnets suspended in a transparent liquid medium, including droplets thereof which may form a discontinuous phase of a continuous hardenable transparent film. My U.S. Pat. No. 4,211,668 discloses a process of making microcapsules having transparent capsule shells and containing a hydrophilic liquid in which rotatable color-coded micromagnets may be suspended. Further, my U.S. Pat. No. 4,232,084 discloses a hardened transparent sheet comprising a binder and hardened microcapsules, the microcapsules containing rotatable viewable color-coded micromagnets dispersed in a liquid. As discussed throughout these patents, the micromagnets have at least two contrasting colors and are magnetically responsive.
The disclosures of all of the above-mentioned patents are incorporated herein by reference.